Nitric oxide mediates isoflavone accumulation and the antioxidant system enhancement in soybean sprouts

Novel strategy to raise the content of aglycone isoflavones in soymilk and gel: Effect of germination on the physicochemical properties

Germination holds the key to nutritional equilibrium in plant grains. In this study, the effect of soybean germination on the processing of soymilk (SM) and glucono-δ-lactone (GDL) induced soymilk gel (SG) was investigated. Germination promoted soybean sprout (SS) growth by activating the energy metabolism system. The energy metabolism was high during the three-day germination and was the most vigorous on the second day of germination. After germination, protein dissolution was improved in SM, and endogenous enzymes produced small molecule proteins. Small molecule proteins were more likely to aggregate to produce SM protein particles. Germination increased the water-holding capacity of SG induced by GDL but weakened the strength. Furthermore, the dynamic fluctuations in isoflavone content were closely monitored throughout the processing of soybean products, including SS, SM, and SG. Although the total amount of isoflavones in SM and SG processed from germinated soybeans decreased, a significant enrichment in the content of aglycone isoflavones was observed. The content of aglycone isoflavones in SG processed from germinated soybeans on the second day of germination was 736.17 ± 28.49 µg/g DW, which was 83.19 % higher than that of the control group. This study demonstrates that germination can enhance the nutritional value of soybean products, providing innovative opportunities for the development of health-promoting soybean-based products.

Refrigerated storage stimulates isoflavone and γ-aminobutyric acid accumulation in germinated soybeans

This study aims to investigate the quality changes of germinated soybeans during refrigerated storage (4 °C), with an emphasis on the stimulatory effect of refrigeration on their special functional compounds. After germinating for two days, germinated soybeans were stored at 4 °C for seven days, while the germinated soybeans stored at 25 °C served as control group. The results showed that refrigerated storage significantly affected the physiological changes in germinated soybeans. The weight loss rate, browning rate, malondialdehyde (MDA) content and H2O2 content all decreased dramatically during refrigerated storage compared to the control group. The total phenolic and total flavonoid contents of germinated soybeans under refrigeration exhibited a trend of increasing and then decreasing over time. Additionally, during refrigerated storage, the total isoflavone content reached a peak of 8.72 g/kg on the fifth day, in which the content of daidzein and glycitin increased by 45% and 49% respectively, when compared with the control group. Moreover, the content of γ-aminobutyric acid (GABA) peaked on the first day, and kept a high level during storage. In which, the refrigerated group was 2.35-, 2.88-, 1.67-fold respectively after storage for three to seven days. These results indicated that refrigeration stimulated the biosynthesis of isoflavones and GABA in germinated soybeans during storage. More importantly, there was a sequential difference in the timing of the stimulation of the two functional components under refrigeration.

Transcriptomic and physiological analysis of the response of Spirodela polyrrhiza to sodium nitroprusside

BACKGROUND

Spirodela polyrrhiza is a simple floating aquatic plant with great potential in synthetic biology. Sodium nitroprusside (SNP) stimulates plant development and increases the biomass and flavonoid content in some plants. However, the molecular mechanism of SNP action is still unclear.

RESULTS

To determine the effect of SNP on growth and metabolic flux in S. polyrrhiza, the plants were treated with different concentrations of SNP. Our results showed an inhibition of growth, an increase in starch, soluble protein, and flavonoid contents, and enhanced antioxidant enzyme activity in plants after 0.025 mM SNP treatment. Differentially expressed transcripts were analysed in S. polyrrhiza after 0.025 mM SNP treatment. A total of 2776 differentially expressed genes (1425 upregulated and 1351 downregulated) were identified. The expression of some genes related to flavonoid biosynthesis and NO biosynthesis was upregulated, while the expression of some photosynthesis-related genes was downregulated. Moreover, SNP stress also significantly influenced the expression of transcription factors (TFs), such as ERF, BHLH, NAC, and WRKY TFs.

CONCLUSIONS

Taken together, these findings provide novel insights into the mechanisms of underlying the SNP stress response in S. polyrrhiza and show that the metabolic flux of fixed CO2 is redirected into the starch synthesis and flavonoid biosynthesis pathways after SNP treatment.

Polyamines inhibit abscisic acid-induced stomatal closure by scavenging hydrogen peroxide

Stomatal closure is regulated by plant hormones and some small molecules to reduce water loss under stress conditions. Both abscisic acid (ABA) and polyamines alone induce stomatal closure; however, whether the physiological functions of ABA and polyamines are synergistic or antagonistic with respect to inducing stomatal closure is still unknown. Here, stomatal movement in response to ABA and/or polyamines was tested in Vicia faba and Arabidopsis thaliana, and the change in the signaling components under stomatal closure was analyzed. We found that both polyamines and ABA could induce stomatal closure through similar signaling components, including the synthesis of hydrogen peroxide (H₂ O₂ ) and nitric oxide (NO) and the accumulation of Ca²⁺ . However, polyamines partially inhibited ABA-induced stomatal closure both in epidermal peels and in planta by activating antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), to eliminate the ABA-induced increase in H₂ O₂ . These results strongly indicate that polyamines inhibit abscisic acid-induced stomatal closure, suggesting that polyamines could be used as potential plant growth regulators to increase photosynthesis under mild drought stress.

Existence of circadian rhythm and its response behavior under different storage conditions of soybean sprouts

The circadian system plays an essential role in plant cells, and numerous physiological events are generally modulated by circadian clock genes. To further improve postharvest handling of fresh produce, it is vital to understanding the behavior of clock gene expression and its underlying interactions with changes in quality. In this study, the effect of temperature and controlled atmosphere storage on the expression of clock genes (GmLCL1, GmPRR7, GmGI, GmTOC1, and GmLUX), postharvest quality characteristics and their related genes in soybean sprouts were investigated. By fitting the obtained gene expression level using the qPCR method with the cosine curve equation, it was successfully found that the circadian rhythm existed under constant dark storage conditions of soybean sprouts. A significant rhythm in clock gene expression was observed in control soybean sprouts. In contrast, low temperature storage diminished the cyclic expression of GmLCL1, GmPRR7, and GmTOC1, which also affected GmGI and GmLUX expression. Additionally, high CO₂ concentrations during storage disturbed the circadian clock by affecting the phase and amplitude of each gene; for low O₂ concentrations, it was only affected by amplitude. Interestingly, low temperature, low O₂, and high CO₂ maintained postharvest quality, including reduced respiration, weight loss and browning incidence. The expression behaviors of postharvest quality attribute-related genes (GmFUM1, GmCS, Gm2-OGDH, GmPPO1, GmPAL) were also influenced by the storage treatments. Overall, the findings first suggest a possible link between clock disruption and postharvest quality maintenance of soybean sprouts.

Say "NO" to plant stresses: Unravelling the role of nitric oxide under abiotic and biotic stress

Nitric oxide (NO) is a diatomic gaseous molecule, which plays different roles in different strata of organisms. Discovered as a neurotransmitter in animals, NO has now gained a significant place in plant signaling cascade. NO regulates plant growth and several developmental processes including germination, root formation, stomatal movement, maturation and defense in plants. Due to its gaseous state, it is unchallenging for NO to reach different parts of cell and counterpoise antioxidant pool. Various abiotic and biotic stresses act on plants and affect their growth and development. NO plays a pivotal role in alleviating toxic effects caused by various stressors by modulating oxidative stress, antioxidant defense mechanism, metal transport and ion homeostasis. It also modulates the activity of some transcriptional factors during stress conditions in plants. Besides its role during stress conditions, interaction of NO with other signaling molecules such as other gasotransmitters (hydrogen sulfide), phytohormones (abscisic acid, salicylic acid, jasmonic acid, gibberellin, ethylene, brassinosteroids, cytokinins and auxin), ions, polyamines, etc. has been demonstrated. These interactions play vital role in alleviating plant stress by modulating defense mechanisms in plants. Taking all these aspects into consideration, the current review focuses on the role of NO and its interaction with other signaling molecules in regulating plant growth and development, particularly under stressed conditions.

Interaction of Gamma-Aminobutyric Acid and Ca2+ on Phenolic Compounds Bioaccumulation in Soybean Sprouts under NaCl Stress

NaCl stress can enhance the accumulation of phenolic compounds in soybean during germination. In the present study, effects of gamma-aminobutyric acid (GABA) and Ca²⁺ on the biosynthesis of phenolic compounds in soybean sprouts germinated with NaCl stress were investigated. Results showed that addition of Ca²⁺ increased the content of total phenolics, phenolic acids, and isoflavonoids in soybean sprouts by ca. 15%, 7%, and 48%, respectively, through enhancing the activities of three key enzymes involved in the biosynthesis. On the other hand, addition of LaCl₃, a calcium channel blocker, inhibited the synthesis of phenolic compounds, indicating that Ca²⁺ plays an important role in the synthesis of these compounds in soybean sprouts. Addition of GABA can increase the content of Ca²⁺ in soybean sprouts by ca. 20% and alleviate the inhibition of LaCl₃ on phenolics biosynthesis in soybean sprouts. Similarly, addition of Ca²⁺ can reverse the inhibition of 3-mercaptopropionate, an inhibitor of endogenous GABA synthesis, on the biosynthesis of phenolic compounds in soybean sprouts under NaCl stress. To conclude, both GABA and Ca²⁺ can enhance the biosynthesis of phenolic compounds in soybean sprouts and there was an interaction between their effects on the promotion of phenolic compounds biosynthesis.

Nitric oxide mediates melatonin-induced isoflavone accumulation and growth improvement in germinating soybeans under NaCl stress

The involvement of nitric oxide (NO) in exogenous melatonin (MT)-induced isoflavone accumulation and growth improvement in NaCl-stressed soybeans was investigated in this study. The results demonstrated that MT increased the activity of nitrate reductase (NR) and upregulated the relative expression of NR1, NR2, and nitric oxide synthase1, which subsequently led to an increase in NO content. MT and sodium nitroprusside (SNP, as an NO donor) markedly increased isoflavone content by enhancing the activities of cinnamic acid 4-hydroxylase (C4H) and phenylalanine ammonia lyase (PAL), and by upregulating gene expression of C4H, Isoflavone synthase, PAL, and Chalcone isomerase 1A, which are involved in isoflavone biosynthesis. Moreover, MT, as well as SNP, improved the growth and biomass of NaCl-treated soybeans by increasing the activities of superoxide dismutase, catalase, and peroxidase, and reducing the accumulation of H₂O₂ and O₂^•- in soybeans under NaCl stress. These MT-induced responses were entirely reversed by the supply of 4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, a specific scavenger of NO), which in turn considerably decreased endogenous NO content. These results suggest that NO acts as an important downstream signal molecule, mediating MT-induced isoflavone accumulation and growth improvement in NaCl-stressed soybeans.

Widely targeted metabolomics analysis characterizes the phenolic compounds profiles in mung bean sprouts under sucrose treatment

Phenolic compounds are one of the wholesome substances of mung bean sprouts, showing numerous health-promoting functions. Here, effects of sucrose on phenolic compounds profiles of mung bean sprouts were investigated. Results showed that the content and composition of phenolic compounds were significantly altered by 1‰ and 5‰ sucrose, respectively. The antioxidant capacity was significantly improved by sucrose. Based on metabolomics, 251 metabolites were detected, of which 106 were phenolic compounds. Correlation analysis showed 21 phenolics were positively correlated with antioxidant capacity. The changes in phenolic composition and antioxidant capacity after sucrose treatment were mainly due to the enrichment of phenolic biosynthesis pathways. Moreover, the gene expression and enzyme activity analysis of key phenolic biosynthetic genes contributed to elucidate the phenolic profile under sucrose treatment. In summary, mung bean sprouts are promising sources of dietary phenolic compounds and sucrose treatment is a good process to produce phenolic-rich mung bean sprouts.

Phenylalanine Ammonia Lyase GmPAL1.1 Promotes Seed Vigor under High-Temperature and -Humidity Stress and Enhances Seed Germination under Salt and Drought Stress in Transgenic Arabidopsis

Seed vigor is an important agronomic attribute, essentially associated with crop yield. High-temperature and humidity (HTH) stress directly affects seed development of plants, resulting in the decrease of seed vigor. Therefore, it is particularly important to discover HTH-tolerant genes related to seed vigor. Phenylalanine ammonia lyase (PAL, EC 4.3.1.24) is the first rate-limiting enzyme in the phenylpropanoid biosynthesis pathway and a key enzyme involved in plant growth and development and environmental adaptation. However, the biological function of PAL in seed vigor remains unknown. Here, GmPAL1.1 was cloned from soybean, and its protein was located in the cytoplasm and cell membrane. GmPAL1.1 was significantly induced by HTH stress in developing seeds. The overexpression of GmPAL1.1 in Arabidopsis (OE) accumulated lower level of ROS in the developing seeds and in the leaves than the WT at the physiological maturity stage under HTH stress, and the activities of SOD, POD, and CAT and flavonoid contents were significantly increased, while MDA production was markedly reduced in the leaves of the OE lines than in those of the WT. The germination rate and viability of mature seeds of the OE lines harvested after HTH stress were higher than those of the WT. Compared to the control, the overexpression of GmPAL1.1 in Arabidopsis enhanced the tolerance to salt and drought stresses during germination. Our results suggested the overexpression of GmPAL1.1 in Arabidopsis promoted seed vigor at the physiological maturation period under HTH stress and increased the seeds' tolerance to salt and drought during germination.

Exogenous melatonin stimulated isoflavone biosynthesis in NaCl-stressed germinating soybean (Glycine max L.)

Melatonin (MT) has gained increasing attention due to its pleiotropic effects. In this study, the function of exogenous MT on the response to NaCl stress and isoflavone biosynthesis in germinating soybeans was investigated. Results showed the exogenous MT (100 μM) application neutralised the negative effects of NaCl stress (60 mM), induced sprout growth, biomass and fluorescence intensity of intracellular free calcium, decreased malondialdehyde, H2O2 content and fluorescence intensity of O2•-, and enhanced superoxide dismutase, catalase and peroxidas activities of germinating soybeans. Meanwhile, total flavonoids and different forms of isoflavone content were enhanced by MT application, not only companied by the up-regulated relative gene expression of cinnamic acid 4-hydroxylase chalcone reductase, chalcone isomerase 1A, isoflavone reductase and isoflavone synthase 1 that involved in isoflavone biosynthesis, but also increased activities of phenylalanine ammonia lyase and 4-coumarate coenzyme A ligase. Given the evidence from the present study, it's proposed that the exogenous MT could relieve NaCl stress and stimulate isoflavone biosynthesis in germinating soybeans.

UV-B- triggered H2O2 production mediates isoflavones synthesis in germinated soybean

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UV-B up-regulated the activity, gene and protein expression of NADPH oxidase.

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UV-B induced H2O2 signal pathway activation.

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H₂O₂ is an essential signaling molecule mediating UV-B-induced isoflavone production.

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H₂O₂ up-regulated activities, gene and protein expression of PAL, CHS, IFS under UV-B.

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The inhibition of DPI on endogenous H2O2 signal pathway reduced isoflavone synthesis.

In this study, the functions of Hydrogen peroxide (H₂O₂) on the synthesis of isoflavones in germinated soybean under UV-B radiation were investigated. Results showed that the activity, gene, and protein expression of NADPH oxidase were up-regulated by 1.46, 6.92, and 1.34 times with UV-B radiation, while endogenous H₂O₂ content was also significantly increased. UV-B radiation and exogenous H₂O₂ treatment significantly increased the activities, gene and protein expression of phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), and isoflavone synthase (IFS) involved in isoflavones synthesis, and there was a synergistic effect with combining treatment. However, these up-regulation effects were suppressed by the supplementary diphenylene iodonium (DPI), which is the inhibitor of NADPH oxidase. Interestingly, the inhibition effect was largely reversed by exogenous H₂O₂, indicating that H₂O₂ was indispensable in regulating the isoflavones synthesis in germinated soybeans under UV-B radiation. Overall, H₂O₂ is an essential signaling molecule, mediating UV-B-induced isoflavone accumulation.

Growth and Biosynthesis of Phenolic Compounds of Canola (Brassica napus L.) to Different Ultraviolet (UV)-B Wavelengths in a Plant Factory with Artificial Light

The application of ultraviolet-B (UV-B) irradiation to supplement visible light as an elicitor to increase bioactive compounds under controlled conditions is increasing. This study aimed to evaluate the effects of UV-B dose and wavelength region (280−300 and 300−320 nm) on the morphological, physiological, and biochemical responses of canola plants (Brassica napus L.). Canola plants (17 days after sowing) were subjected to various UV-B intensities (i.e., 0.3, 0.6, and 0.9 W m−2) and were divided into cut and non-cut treatments for each UV treatment. Plant growth parameters exhibited different trends based on the treated UV irradiation intensity. Plant growth gradually decreased as the UV irradiation intensity and exposure time increased. Despite the same UV irradiation intensity, plant response varied significantly depending on the presence or absence of a short-wavelength cut filter (<300 nm). Canola plants suffered more leaf damage in nonfilter treatments containing shorter wavelengths (280−300 nm). UV treatment effectively activates the expression of secondary metabolite biosynthetic genes, differing depending on the UV irradiation intensity. Our results suggest that both UV irradiation intensity and wavelength should be considered when enhancing antioxidant phytochemicals without inhibiting plant growth in a plant factory with artificial light.

Occurrence of isoflavones in soybean sprouts and strategies to enhance their content: A review

Sprouting is a common strategy to enhance the nutritional value of seeds. Here, all the reports regarding the occurrence of isoflavones in soybean sprouts have been covered for the first time. Isoflavones were detected with concentrations ranging from 1 × 10-2 to 1 × 101  g/kg in soybean sprouts. Isoflavone concentration depends on the cultivar, germination time, part of the sprout, light, and temperature. Aglycon isoflavones increased during germination, especially in the hypocotyl, while 6″-O-malonyl-7-O-β-glucoside isoflavones decreased in the hypocotyl and increased in the cotyledon and root. Cooking reduced total isoflavone content. Regarding the strategies to enhance isoflavone contents, fermentation with Aspergillus sojae and external irradiation with UV-A or far-infrared were the methods that caused the greatest increases in aglycon, 7-O-β-glucoside, and total isoflavones. However, the largest increases in 6″-O-malonyl-7-O-β-glucoside and 6″-O-acetyl-7-O-β-glucosides isoflavones were detected after treatment with chitohexaose and calcium chloride, respectively. PRACTICAL APPLICATION: Soybean sprouts are widely consumed and provide essential proteins, antioxidants, and minerals. They are rich in isoflavones, which exhibit numerous health benefits, and have been studied as alternative therapies for a range of hormone-dependent conditions, such as cancer, menopausal symptoms, cardiovascular disease, and osteoporosis. Despite numerous reports being published to date regarding the occurrence of isoflavones in soybean sprouts, the publications in this field are highly dispersed, and a review has not yet been published. This review aims to (1) highlight the particular isoflavones that have been detected in soybean sprouts and their concentrations, (2) compared the effects of temperature, light, cooking and soybean cultivar affect the isoflavone levels on the different parts of the sprout, and (3) discuss the efficacy of the methods to enhance isoflavone contents. This review will provide a better understanding of the current state of this field of research by comparing the general trends and the different treatments for soybean sprouts.

Melatonin mediates isoflavone accumulation in germinated soybeans (Glycine max L.) under ultraviolet-B stress

Soybean germination under ultraviolet-B (UV-B) radiation stress is a common and effective way to enrich the isoflavone content of sprouts. However, the growth and biomass of germinated soybeans are significantly suppressed using this method. Melatonin (MT), a novel plant biostimulant, not only plays a vital protective role in responses to various abiotic stresses but also regulates the accumulation of secondary metabolites. In the present study, the effects of exogenous MT on the growth and isoflavone metabolism of germinating soybeans exposed to UV-B stress were investigated. Compared to UV-B stress, the application of exogenous MT (25 μM) significantly increased sprout length, fresh weight, Ca2+ influx, and peroxidase activity; markedly decreased the content of malondialdehyde and H2O2 and the fluorescence intensity of H2O2 and O2•-; but had no noticeable effect on the activity of superoxide dismutase and catalase during germination. Moreover, the content of total flavonoids and isoflavone monomers (including daidzein, genistein, daidzin, glycitin and genistin) in 4-day-old germinated soybeans was significantly enhanced by MT application under UV-B stress and was not only companied by dramatically increased phenylalanine ammonia lyase activity, but also by markedly increased relative expression levels of phenylalanine ammonia lyase1, chalcone synthase, isoflavone reductase and flavanone 3-hydroxylase that are involved in the isoflavone biosynthesis pathway. The inhibitory effects of UV-B stress on the growth and biomass of germinated soybeans were alleviated with exogenous MT. MT enhanced the content of total flavonoids and isoflavone monomers under UV-B stress by increasing the activity and relative gene expression level of critical isoflavone biosynthesis-related enzymes.

Seed Treatment with Illite Enhanced Yield and Nutritional Value of Soybean Sprouts

Soybean sprouts, a nutritional food product, can contribute to food security because they can be grown within a week and do not require sophisticated technology. The yield and quality of soybean sprouts are influenced by various factors, including seed priming and growing conditions. The objective of this study was to investigate the effects of seed soaking in different concentrations of illite, a clay mineral, on the yield and quality of soybean sprouts. Soybean seeds soaked in five concentrations (0.5%, 1%, 3%, 5%, and 10%, w/v) of illite or tap water for 8 h were named IP-0.5, IP-1, IP3, IP-5, IP-10, and control, respectively. The highest sprout yield was found in IP-3, followed by IP-1, and IP-5, which had 11.1%, 8.8%, and 7.4% increments, respectively, compared to the control. The content of vitamin C, mineral element, isoflavone, total polyphenol, and total flavonoid was higher in many of the illite-treated soybean sprouts than in the control. The overall results indicated that pre-soaking soybean seeds in lower concentrations (0.5-3%, w/v) of illite could be helpful to enhance the yield and nutritional value of soybean sprouts in an easy and inexpensive way.

Recent advances on the roles of flavonoids as plant protective molecules after UV and high light exposure

Flavonoids are plant specialized metabolites that consist of one oxygenated and two aromatic rings. Different flavonoids are grouped according to the oxidation degree of the carbon rings; they can later be modified by glycosylations, hydroxylations, acylations, methylations, or prenylations. These modifications generate a wide collection of different molecules which have various functions in plants. All flavonoids absorb in the UV wavelengths, they mostly accumulate in the epidermis of plant cells and their biosynthesis is generally activated after UV exposure. Therefore, they have been assumed to protect plants against exposure to radiation in this range. Some flavonoids also absorb in other wavelengths, for example anthocyanins, which absorb light in the visible part of the solar spectrum. Besides, some flavonoids show antioxidant properties, that is, they act as scavengers of reactive oxygen species that could be produced after high fluence UV exposure. However, to date most reports were based on in vitro studies, and there is very little in vivo evidence of how their roles are carried out. In this review we first summarize the biosynthetic pathway of flavonoids and their characteristics, and we describe recent advances on the investigation of the role of three of the most abundant flavonoids: flavonols, flavones, and anthocyanins, protecting plants against UV exposure and high light exposure. We also present examples of how using UV-B supplementation to increase flavonoid content, is possible to improve plant nutritional and pharmaceutical values.

The Drought-Mediated Soybean GmNAC085 Functions as a Positive Regulator of Plant Response to Salinity

Abiotic stress factors, such as drought and salinity, are known to negatively affect plant growth and development. To cope with these adverse conditions, plants have utilized certain defense mechanisms involved in various aspects, including morphological, biochemical and molecular alterations. Particularly, a great deal of evidence for the biological importance of the plant-specific NAM, ATAF1/2, CUC2 (NAC) transcription factors (TFs) in plant adaptation to abiotic stress conditions has been reported. A previous in planta study conducted by our research group demonstrated that soybean (Glycine max) GmNAC085 mediated drought resistance in transgenic Arabidopsis plants. In this study, further characterization of GmNAC085 function in association with salt stress was performed. The findings revealed that under this condition, transgenic soybean plants overexpressing GmNAC085 displayed better germination rates than wild-type plants. In addition, biochemical and transcriptional analyses showed that the transgenic plants acquired a better defense system against salinity-induced oxidative stress, with higher activities of antioxidant enzymes responsible for scavenging hydrogen peroxide or superoxide radicals. Higher transcript levels of several key stress-responsive genes involved in the proline biosynthetic pathway, sodium ion transporter and accumulation of dehydrins were also observed, indicating better osmoprotection and more efficient ion regulation capacity in the transgenic lines. Taken together, these findings and our previous report indicate that GmNAC085 may play a role as a positive regulator in plant adaptation to drought and salinity conditions.

GABA Regulates Phenolics Accumulation in Soybean Sprouts under NaCl Stress

NaCl stress causes oxidative stress in plants; γ-aminobutyric acid (GABA) could alleviate such abiotic stress by enhancing the synthesis of phenolics, but the underlying mechanism is not clear. We investigated the effects of GABA on phenolics accumulation in soybean sprouts under NaCl stress by measuring changes in the content of physiological biochemicals and phenolic substances, in the activity and gene expression of key enzymes, and in antioxidant capacity. GABA reduced the oxidative damage in soybean sprouts caused by NaCl stress and enhanced the content of total phenolics, phenolic acids, and isoflavones by 16.58%, 22.47%, and 3.75%, respectively. It also increased the activities and expression of phenylalanine ammonia lyase, cinnamic acid 4-hydroxylase, and 4-coumarate coenzyme A ligase. Furthermore, GABA increased the activity of antioxidant enzymes and the antioxidant capacity. These events were inhibited by 3-mercaptopropionate (an inhibitor for GABA synthesis), indicating that GABA mediated phenolics accumulation and antioxidant system enhancement in soybean sprouts under NaCl stress.

Plant sprout foods: Biological activities, health benefits, and bioavailability

Plant sprout foods exhibit a lot of biological activities including anti-inflammatory, antioxidative, anticancer, antidiabetes, anti-infection, and antiviral activities. Up to the present moment, plant sprout foods have received much attention due to their abundance, good bioavailability, and health benefits for human. This review highlights the biological activities of different plant sprout foods (viz., broccoli sprout, buckwheat sprout, wheat sprout, mung bean sprout, soybean sprout, and adkuzi bean sprout) using in vitro model, animal model, and human model. Furthermore, the bioavailability of plant sprout foods is also discussed. PRACTICAL APPLICATIONS: A review of the literature was conducted to biological activities of plant sprout foods, in addition to a summary of health benefits and bioavailability of sprout foods. Several biological activities of plant sprout foods with in vitro and in vivo evidence are currently unexplored in clinical trials, because the effects of sprout foods on human tissues and cells measured by tube test do not recapitulate the actual in vivo effects. Moreover, the safety of chemoprevention strategies using sprout foods that to protect against environmental exposures and other oxidative stress-related pathologies is important. Further research is warranted to evaluate bioavailability of individual forms.

Blue and UV-B light synergistically induce anthocyanin accumulation by co-activating nitrate reductase gene expression in Anthocyanin fruit (Aft) tomato

The tomato accession LA1996, which carries a dominant allele of anthocyanin fruit (Aft) locus, accumulates anthocyanins in the epidermis of fruits when exposed to sunlight. The involvement of blue, UV-A, UV-B and a combination of these wavelengths on anthocyanin accumulation and the molecular mechanism of their regulation was investigated in LA1996. The most effective treatment for inducing anthocyanin biosynthesis in Aft fruits was co-irradiation with blue and UV-B (blue + UV-B) light. Finding the correlated genes is an important approach towards understanding their molecular mechanisms. In the present study, the nitrate reductase (NR) gene SlNIA was isolated using RNA-seq profiling of Aft fruits given different light treatments. The functions of NR-mediated anthocyanin induction by blue + UV-B were confirmed using a series of chemical treatments, followed by assessment of NR activity and nitric oxide (NO) detection. The expression of NR was highly induced by blue + UV-B, and this specificity was also confirmed with the enzyme activity of NR and the NO concentration. The NR inhibitors, which reduce NO generation, the expression levels of anthocyanin related genes and decreased anthocyanin accumulation in LA1996. Our results suggest that NR plays a key role in blue + UV-B-mediated anthocyanin accumulation in LA1996 fruits.

Pu-erh Tea Extract Treatment Could Be an Efficient Way to Enhance the Yield and Nutritional Value of Soybean Sprout

Soybean sprouts are one of the most inexpensive and nutritious food items that can be easily grown year-round. Several studies have been conducted to increase their yield and nutritional values. This study was carried out to examine the effects of Pu-erh tea extracts on the production and nutrients content of soybean sprouts. Soybean seeds were soaked in 1%, 2%, or 3% (w/v) tea extracts, or tap water, before keeping for sprout cultivation; the sprout samples were named PE-1, PE-2, PE-3, and the control, respectively. The sprout yields were increased by up to 17% in PE-2 and PE-3 than in the control. The vitamin C, total free amino acid, total mineral, total isoflavone, total polyphenol, and flavonoid contents as well as the antioxidant potentials of the tea extract-treated sprouts were higher than those of the control. The results indicated that pre-soaking soybean seeds in 2% Pu-erh tea extracts could offer an easy, inexpensive, and efficient way to improve the yield and nutritional value of soybean sprouts.

Nitric oxide regulates ganoderic acid biosynthesis by the S-nitrosylation of aconitase under heat stress in Ganoderma lucidum

Nitric oxide (NO) is an important signalling molecule in stress response of organisms. We previously reported that NO decreases heat stress (HS)-induced ganoderic acid (GA) accumulation in Ganoderma lucidum. To explore the mechanisms by which NO modulates GA biosynthesis under HS, the effect of NO on the reactive oxygen species (ROS) content was examined. The results showed that NO decreased the production of mitochondrial ROS (mitROS) by 60% under HS. Further research revealed that NO reduced the mitROS content by inhibiting aconitase (Acon) activity. The GA content in Acon-silenced (Aconi) strains treated with NO donor did not differ significantly from that in untreated Aconi strains. To study the mechanism by which Acon activity is inhibited, the S-nitrosylation level of Acon was determined. Biotin-switch technology and mass spectrometry analysis were used to show that Acon is S-nitrosylated at the Cys-594 amino acid residue. Substitution of Cys-594 with a Ser, which cannot be S-nitrosylated, abolished the responsiveness of Acon to the NO-induced reduction in its enzymatic activity. These findings demonstrate that NO inhibits Acon activity through S-nitrosylation at Cys-594. In summary, these findings describe mechanism by which NO regulates GA biosynthesis via S-nitrosylation of Acon under HS condition in G. lucidum.

Isoflavone accumulation and the metabolic gene expression in response to persistent UV-B irradiation in soybean sprouts

This study investigated the effects of persistent ultraviolet B (UV-B) irradiation on isoflavone accumulation in soybean sprouts. Three malonyl isoflavones were increased by UV-B. Malonylgenistin specifically accumulated upon UV-B exposure, whereas the other isoflavones were significantly increased under both dark conditions and UV-B exposure. The results of isoflavone accumulation to UV-B irradiation time were observed as following: acetyl glycitin rapidly increased and then gradually decreased; malonyl daidzin and malonyl genistin were highly accumulated within an intermediate period; genistein and daidzin were gradually maximized; daidzin, glycitin, genistein, and malonyl glycitin did not increase; and glycitin, acetyl daidzin, and acetyl genistin exhibited trace amounts. Transcriptional analysis of isoflavonoid biosynthetic genes demonstrated that most metabolic genes were highly activated in response to UV-B 24 and UV-B 36 treatments. In particular, it was found that GmCHS6, GmCHS7, and GmCHS8 genes among the eight known genes encoding chalcone synthase were specifically related to UV-B response.

Mechanisms and Role of Nitric Oxide in Phytotoxicity-Mitigation of Copper

Phytotoxicity of metals significantly contributes to the major loss in agricultural productivity. Among all the metals, copper (Cu) is one of essential metals, where it exhibits toxicity only at its supra-optimal level. Elevated Cu levels affect plants developmental processes from initiation of seed germination to the senescence, photosynthetic functions, growth and productivity. The use of plant growth regulators/phytohormones and other signaling molecules is one of major approaches for reversing Cu-toxicity in plants. Nitric oxide (NO) is a versatile and bioactive gaseous signaling molecule, involved in major physiological and molecular processes in plants. NO modulates responses of plants grown under optimal conditions or to multiple stress factors including elevated Cu levels. The available literature in this context is centered mainly on the role of NO in combating Cu stress with partial discussion on underlying mechanisms. Considering the recent reports, this paper: (a) overviews Cu uptake and transport; (b) highlights the major aspects of Cu-toxicity on germination, photosynthesis, growth, phenotypic changes and nutrient-use-efficiency; (c) updates on NO as a major signaling molecule; and (d) critically appraises the Cu-significance and mechanisms underlying NO-mediated alleviation of Cu-phytotoxicity. The outcome of the discussion may provide important clues for future research on NO-mediated mitigation of Cu-phytotoxicity.

Comparative Analysis of Phenolic Compound Profiles, Antioxidant Capacities, and Expressions of Phenolic Biosynthesis-Related Genes in Soybean Microgreens Grown under Different Light Spectra

Light-emitting diode (LED) based light sources, which can selectively and quantitatively provide different spectra, have been frequently applied to manipulate plant growth and development. In this study, the effects of different LED light spectra on the growth, phenolic compounds profile, antioxidant capacity, and transcriptional changes in genes regulating phenolic biosynthesis in soybean microgreens were investigated. The results showed that light illumination decreased the seedling length and yield but increased phenolic compound content. Blue light and ultraviolet-A (UV-A) induced significant increases in total phenolic and total flavonoid content, as compared with the white light control. Sixty-six phenolic compounds were identified in the soybean samples, of which isoflavone, phenolic acid, and flavonol were the main components. Ten phenolic compounds obtained from the orthogonal partial least-squares discriminant analysis (OPLS-DA) were reflecting the effect of light spectra. The antioxidant capacity was consistent with the phenolic metabolite levels, which showed higher levels under blue light and UV-A compared with the control. The highest transcript levels of phenolic biosynthesis-related genes were observed under blue light and UV-A. The transcript levels of GmCHI, GmFLS, and GmIOMT were also upregulated under far-red and red light. Taken together, our findings suggested that the application of LED light could pave a green and effective way to produce phenolic compound-enriched soybean microgreens with high nutritional quality, which could stimulate further investigations for improving plant nutritional value and should have a wide impact on maintaining human health.

iTRAQ-based proteomic analysis reveals changes in response to sodium nitroprusside treatment in soybean sprouts

In recent years, nitric oxide (NO) has been considered a plant signaling compound involved in antioxidant systems and flavonoid production enhancement. Nevertheless, its mechanism of action, from the perspective of protein expression, remains largely unknown. In this study, isobaric tags for relative and absolute quantitation (iTRAQ) was employed to investigate NO donor sodium nitroprusside treatment-induced proteomic changes in soybean sprouts. Among the 3033 proteins identified, compared with the control, sodium nitroprusside treatment up- and down-regulated 256 proteins. These proteins were involved in antioxidant system pathways, such as the thioredoxin, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR) and lipoxygenase (LOX) pathways, including allene oxide synthase and lipoxygenase. In addition, heat shock proteins (HSPs) and flavonoid biosynthetic proteins, such as cinnamate 4-hydroxylase, chalcone isomerase, chalcone synthase, isoflavone synthase and isoflavone reductase, were also modulated in response to sodium nitroprusside treatment.

Neuroprotective effects of a protein tyrosine phosphatase inhibitor against hippocampal excitotoxic injury

Neuronal excitotoxicity is the neuronal cell death arising from prolonged exposure to glutamate and the associated excessive influx of ions into the cell. Sodium orthovanadate (Na₃VO₄,) competitively inhibits the protein tyrosine phosphatases that affect intracellular protein phosphorylation. No study has examined the role of protein tyrosine phosphatases in kainic acid (KA)-induced excitotoxic injury using sodium orthovanadate. Thus, the present study was conducted to determine the neuroprotective effects of sodium orthovanadate on KA-induced neuronal death in organotypic hippocampal slice culture. We also performed an in vivo electrophysiology study in Sprague-Dawley rats to observe the function of surviving cells after sodium orthovanadate treatment in KA-induced excitotoxicity. Rats were anaesthetized with sodium pentobarbital and KA was injected unilaterally in CA3 of the hippocampus by microinjection-cannula. Neuronal cell death, as assessed by propidium iodide uptake, was reduced by 10 and 25 μM sodium orthovanadate treatment (24 and 48 h) compared with the KA-only group. Sodium orthovanadate enhanced survival signals by increasing levels of phospho-Akt and superoxide dismutase. In addition, sodium orthovanadate treatment reduced calcineurin level for neuronal protection, which regulates activation of cellular calcium caused by KA-induced injury. In vivo results showed that sodium orthovanadate treatment elicited resistance to KA-induced behavior seizures and significantly reduced the duration of epileptiform discharges. In addition, sodium orthovanadate treatment (25 mM) significantly prevented the increase in power spectra induced by KA injection. These results suggest that sodium orthovanadate decreases the acute effects of KA, thereby inducing neuroprotective effects with reduced reactive oxygen species and cellular Ca²⁺. Thus, sodium orthovanadate may protect hippocampal neurons against excitotoxicity, and surviving neurons may function to reduce seizures.

Postharvest UV-B Irradiation Stimulated Ginsenoside Rg1 Biosynthesis through Nitric Oxide (NO) and Jasmonic Acid (JA) in Panax quinquefolius Roots

The study highlights the influence and signal transduction mechanism of postharvest UV-B on the production of Rg1 in Panax quinquefolius roots during the drying process. The results showed that postharvest UV-B irradiation induced generation of nitric oxide (NO), jasmonic acid (JA), and ginsenoside Rg1 of P. quinquefolius roots. The UV-B-induced increase of Rg1 was suppressed by NO-specific scavenger (cPTIO) and NOS inhibitors (PBITU), JA synthesis inhibitor (SHAM), and JA synthesis inhibitor (PrGall), indicating that NO and JA played essential parts in UV-B-induced Rg1. External NO inhibitors treatment inhibited UV-B-induced accumulation of NO and JA, which suggested that NO was located upstream of the JA signal pathway. NO-caused Rg1 was inhibited by SHAM and PrGall, implying JA participated in transmitting signal NO to Rg1 accumulation. In other words, NO mediated the postharvest UV-B-induced Rg1 accumulation by the JA-dependent pathway in P. quinquefolius roots during the drying process, which helps us understand the underlying mechanisms involved in UV-B-induced Rg1 production and provides information helpful for P. quinquefolius production.

Overexpression of a soybean 4-coumaric acid: coenzyme A ligase (GmPI4L) enhances resistance to Phytophthora sojae in soybean

Phytophthora root and stem rot of soybean (Glycine max (L.) Merr.) caused by Phytophthora sojae is a destructive disease worldwide. The enzyme 4-coumarate: CoA ligase (4CL) has been extensively studied with regard to plant responses to pathogens. However, the molecular mechanism of the response of soybean 4CL to P. sojae remains unclear. In a previous study, a highly upregulated 4CL homologue was characterised through suppressive subtractive hybridisation library and cDNA microarrays, in the resistant soybean cultivar 'Suinong 10' after infection with P. sojae race 1. Here, we isolated the full-length EST, and designated as GmPI4L (P. sojae-inducible 4CL gene) in this study, which is a novel member of the soybean 4CL gene family. GmPI4L has 34-43% over all amino acid sequence identity with other plant 4CLs. Overexpression of GmPI4L enhances resistance to P. sojae in transgenic soybean plants. The GmPI4L is located in the cell membrane when transiently expressed in Arabidopsis protoplasts. Further analyses showed that the contents of daidzein, genistein, and the relative content of glyceollins are significantly increased in overexpression GmPI4L soybeans. Taken together, these results suggested that GmPI4L plays an important role in response to P. sojae infection, possibly by enhancing the content of glyceollins, daidzein, and genistein in soybean.

iTRAQ-based proteomic analysis reveals changes in response to UV-B treatment in soybean sprouts

It has been shown that 15 μW·cm-2 UV-B radiation has the most pronounced effects on γ-aminobutiric acid (GABA), inositol 1,4,5-trisphosphate (IP3) and abscisic acid (ABA) accumulation in 4-day-old soybean sprouts. Nevertheless, its mechanism of action, from the perspective of protein expression, remains largely unknown. In this study, isobaric tags for relative and absolute quantitation (iTRAQ) were employed to investigate UV-B treatment-induced proteomic changes in soybean sprouts. Results showed that UV-B treatment effectively regulated proteins involved in GABA biosynthesis, such as glutamate synthase, glutamate decarboxylase (GAD), methionine synthetase, 5-methyltetrahydropteroyltriglutamate--homocysteine methyltransferase, aminoaldehyde dehydrogenase (AMADH) and inositol phosphate metabolism pathways, including phosphoinositide phospholipase C (PI-PLC), purple acid phosphatase (PAP) and inositol polyphosphate 5-phosphatase. In addition, proteins involved in ABA biosynthesis and signal transduction, such as 9-cis-epoxycarotenoid dioxygenase (NCED), abscisic-aldehyde oxidase (AO), SNF1-related protein kinase (SnRK), protein phosphatase 2C (PP2C), guanine nucleotide-binding protein and calreticulin-3, were also modulated under UV-B treatment.

Cyclic GMP mediates abscisic acid-stimulated isoflavone synthesis in soybean sprouts

The influences of abscisic acid (ABA)-guanosine 3',5'-cyclic monophosphate (cGMP) on UV-B treatment-stimulated isoflavone synthesis in soybean sprouts was explored. It turned out that ABA, with cGMP, up-regulated gene expression and activity of chalcone synthase (CHS) and isoflavone synthase (IFS), and subsequently induced isoflavone biosynthesis under UV-B treatment. Furthermore, data obtained from the isobaric tags for relative and absolute quantification (iTRAQ) analysis showed that there were two core components in ABA response: SNF1-related protein kinase (SnRK) and type 2C protein phosphatase (PP2C), were up and down regulated after UV-B treatment, respectively. UV-B exposure stimulated increment in guanine nucleotide-binding protein and calreticulin expression. Additionally, CHS and IFS protein expression were up regulated under UV-B stress. Overall, UV-B-induced ABA resulted in PP2C inhibition and SnRK2 activation, and up-regulated CHS and IFS expression, leading to enhancement of isoflavone accumulation. cGMP and calreticulin as downstream messengers, mediated ABA-stimulated isoflavone biosynthesis after UV-B exposure.

UV-B mediates isoflavone accumulation and oxidative-antioxidant system responses in germinating soybean

This study investigated the relationships among UV-B radiation dose, isoflavone monomers and the oxidative-antioxidant system in germinating soybean. Results showed that the isoflavone monomers content showed a good fit to the quadratic model with UV-B radiation dose, except for aglycones. UV-B decreased phenylalanine content and up-regulated the key enzymes activities in isoflavone biosynthesis. H2O2, electrolyte leakage, malondialdehyde, T22 and M22 were increased, while T23 and M23 decreased. Microscopic analysis showed excess UV-B radiation resulted in the reduced cell volume, irregular cell shape, and increased cell space. The antioxidant enzymes activities were enhanced by UV-B. These results demonstrated that UV-B could trigger the formation of H2O2, resulting in the oxidative stress. Thus, the antioxidant system, including the enzymatic (enhanced the antioxidant enzymes activities) and nonenzymatic (accumulated isoflavones) were activated to minimize oxidative damage. This study provides theoretical basis for enhancing isoflavone monomer accumulation in plant-source foods by UV-B.

Effects of UV-B radiation on the isoflavone accumulation and physiological-biochemical changes of soybean during germination: Physiological-biochemical change of germinated soybean induced by UV-B

In this study, the effects of UV-B radiation on the isoflavones accumulation, physiological and nutritional quality, water status, and characteristics of proteins in germinated soybeans were investigated. The results showed that isoflavones content in soybeans increased with appropriate intensity and time of UV-B radiation and decreased with excessive treatment. Fresh weight, length, free amino acids, reducing sugar contents and bulk water (T23) in germinated soybeans decreased with increasing radiation time, indicating that UV-B inhibited the growth and nutrients metabolism of soybean during germination. Cell damage was detected in germinated soybeans with excessive UV-B radiation, as shown by the black spots in cotyledons and the increased intercellular water determined by LF-NMR. Germination resulted in an increase in random coil structures, while UV-B radiation induced no obvious changes in FT-IR spectrum and protein conformation of soybeans. Both UV-B radiation and germination caused the increase in soluble proteins, especially in 1.0-75.0 kDa fraction.

GSK-3 mediates NO-cGMP-induced isoflavone production in soybean sprouts

The role of glycogen synthase kinase-3 (GSK-3) in the nitric oxide-guanosine 3',5'-cyclic monophosphate (NO-cGMP)-induced isoflavone production in soybean sprouts was examined. Inhibitors and donors of NO, cGMP, and GSK-3 inhibitor were added to UV-B irradiated sprouts. Results showed that NO, with cGMP, induced the expression of GSK-3 under UV-B radiation. Protein kinase G (PKG) was shown to be involved in NO-cGMP-induced GSK-3 activation. GSK-3 elevated activity and expression levels of chalcone synthase (CHS) and isoflavone synthase (IFS), and increased isoflavone accumulation.

Inhibitory effect and mechanism of Tagetes erecta L. fungicide on Fusarium oxysporum f. sp. niveum

Botanical fungicides comprise attractive alternatives to chemical fungicides because of their environmental compatibility. Flavonoids extracted from Tagetes erecta L. have an inhibitory effect on fusarium wilt in watermelons caused by Fusarium oxysporum f. sp. niveum (FON). In this study, we synthesized one of these flavonoids, 2,5-dicyclopentylidene cyclopentanone (Tagetes erecta L. fungicide (TEF)) and assessed its activity against FON. In vitro, TEF inhibited FON growth and killed FON cells directly. TEF also affected FON cell physiology and mycelial structure. In watermelon plants with fusarium wilt, TEF protected the leaf cell structure and improved the germination rate of infected seeds while increasing overall plant resistance. A TEF-resistant mutant (FONM) was created by chemical mutagenesis. FON and FONM were analysed using iTRAQ and RNA-Seq, which identified 422 differentially expressed proteins and 7817 differentially expressed mRNAs in the proteome and transcriptome, respectively. The FONM mutations caused changes in the cell membrane and cell wall, which may constitute the site of action of TEF. Together, these results demonstrate that TEF could effectively control the watermelon fusarium wilt caused by FON, possibly through the inhibition of sterol biosynthesis. The data presented here suggest that TEF represents a new potential botanical anti-fungal drug.

Persimmon Fruit Powder May Substitute Indolbi, a Synthetic Growth Regulator, in Soybean Sprout Cultivation

Soybean sprouts are a major food item in Korea. Various studies have been carried out to enhance their yield and nutritional values. The objective of the present study was to examine the influence of persimmon fruit powder and Indolbi, a synthetic plant growth regulator, on the yield and nutritional value of soybean sprouts. Seeds were soaked in tap water containing 0.5%, 1.0%, 2.5% and 5.0% (w/v) persimmon fruit powder and the samples were named as PT-1, PT-2, PT-3, and PT-4, respectively. The yield increment was almost doubled in PT-3 and PT-4 than in the Indolbi treated sprouts on basis of the control. Vitamin C, isoflavones, and total phenolic contents as well as antioxidant potentials (determined by 1,1-diphenyl-2-picrylhydrazyl and superoxide anion radical scavenging assays) were also significantly (p < 0.05) higher in PT-3 compared to the Indolbi treatment and the control. However, total free amino acid and magnesium contents of Indolbi- applied sprouts were higher than in the fruit powder treatments. The overall results of the present study showed that persimmon fruit powder can be an option to enhance the yield and nutritional value of soybean sprouts since, due to potential health hazards, the use of synthetic chemicals like Indolbi is less preferred than the natural products.

Phenylalanine ammonia-lyase2.1 contributes to the soybean response towards Phytophthora sojae infection

Phytophthora root and stem rot of soybean [Glycine max (L.) Merr.] caused by Phytophthora sojae is a destructive disease worldwide. Phenylalanine ammonia-lyase (PAL) is one of the most extensively studied enzymes related to plant responses to biotic and abiotic stresses. However, the molecular mechanism of PAL in soybean in response to P. sojae is largely unclear. Here, we characterize a novel member of the soybean PAL gene family, GmPAL2.1, which is significantly induced by P. sojae. Overexpression and RNA interference analysis demonstrates that GmPAL2.1 enhances resistance to P. sojae in transgenic soybean plants. In addition, the PAL activity in GmPAL2.1-OX transgenic soybean is significantly higher than that of non-transgenic plants after infection with P. sojae, while that in GmPAL2.1-RNAi soybean plants is lower. Further analyses show that the daidzein, genistein and salicylic acid (SA) levels and the relative content of glyceollins are markedly increased in GmPAL2.1-OX transgenic soybean. Taken together, these results suggest the important role of GmPAL2.1 functioning as a positive regulator in the soybean response to P. sojae infection, possibly by enhancing the content of glyceollins, daidzein, genistein and SA.

IP3 Mediates Nitric Oxide-Guanosine 3',5'-Cyclic Monophosphate (NO-cGMP)-Induced Isoflavone Accumulation in Soybean Sprouts under UV-B Radiation

In this study, to investigate the role of inositol 1,4,5-trisphosphate (IP3) in nitric oxide-guanosine 3',5'-cyclic monophosphate (NO-cGMP)-induced isoflavone accumulation in soybean sprouts under UV-B radiation, the sprouts were treated with donors and inhibitors of NO and cGMP as well as IP3 inhibitor. Results showed that NO, with cGMP as a second messenger, stimulates IP3 accumulation under UV-B radiation. Consistent with the increase in IP3 content, the up-regulation of gene and protein expression of phosphoinositide-specific phospholipase C (PI-PLC) in response to sodium nitroprusside (SNP) (exogenous NO donor) and 8-Br-cGMP (cGMP analogue) was also observed. In addition, protein kinase G (PKG) participated in NO-cGMP-induced IP3 production. IP3 induced by the NO-cGMP pathway was involved in isoflavone synthesis by elevating the activity and gene and protein expressions of chalcone synthase (CHS) and isoflavone synthase (IFS). Overall, IP3 mediates NO-cGMP-induced isoflavone accumulation in soybean sprouts under UV-B stress.

Cyclic ADP-ribose and IP3 mediate abscisic acid-induced isoflavone accumulation in soybean sprouts

In this study, the roles of ABA-cADPR-Ca2+ and ABA-IP3-Ca2+ signaling pathways in UV-B-induced isoflavone accumulation in soybean sprouts were investigated. Results showed that abscisic acid (ABA) up regulated cyclic ADP-ribose (cADPR) and inositol 1,4,5-trisphosphate (IP3) levels in soybean sprouts under UV-B radiation. Furthermore, cADPR and IP3, as second messengers of UV-B-triggered ABA, induced isoflavone accumulation by up-regulating proteins and genes expression and activity of isoflavone biosynthetic-enzymes (chalcone synthase, CHS; isoflavone synthase, IFS). After Ca2+ was chelated by EGTA, isoflavone content decreased. Overall, ABA-induced cADPR and IP3 up regulated isoflavone accumulation which was mediated by Ca2+ signaling via enhancing the expression of proteins and genes participating in isoflavone biosynthesis in soybean sprouts under UV-B radiation.